Our attitude towards risk shapes nearly every aspect of our behavior. It affects our willingness to take drugs of abuse, to make efficient financial investments, and to select amongst healthcare options. We know that these attitudes change over the lifespan and that these changes make us vulnerable in different ways as we age. Adolescents engage in risky behaviors that hugely increase their mortality rates. Elders typically show the opposite profile, avoiding risky behaviors to a fault. But what is it about our behavior that changes as we age? What specific behavioral propensities and neurobiological features of aging can account for the changing attitudes we take towards risks? In this application we propose to combine economic, psychological and neurobiological approaches to the study of risky behavior in an effort to paint a portrait of risk attitudes across the lifespan at the behavioral and neural levels. Behavioral economic analyses suggests that risk-taking behavior results from the three largely independent attitudes towards risks: (1) Technical risk-aversion, which reflects a trade- off between the probability of gains or losses and the magnitude of those gains and losses, (2) Ambiguity aversion, which reflects the subject's sensitivity to uncertainty, and (3) Loss aversion, which reflects a subject's differential sensitivity to losses and gains. We hypothesize that the reduction in risk-taking behavior across the lifespan that is widely observed is primarily due to an increase in ambiguity aversion, rather than to an increase in risk or loss attitudes. Further, we hypothesize that, if anything, humans should become less technically risk averse and loss averse as they age. At the neural level, we also know that there are clear structural patterns in brain development that may well underlie these behavioral changes observed across the lifespan. Of particular interest to our hypothesis is the observation that frontal regions mature late, actually thinning during development and actually continue to thin throughout the lifespan. Activational patterns fronto-cortical decision areas also change throughout the lifespan. These data suggest that both morphologic and functional properties of the frontal cortex may contribute to these changes in risk-related behavior over the lifespan, a hypothesis we propose to test with a mixture of behavioral and functional imaging techniques.